A torque limiting coupling includes a longitudinal axis around which the torque limiting coupling is rotatably arranged. A coupling hub has circumferentially distributed through openings. Drivers are displaceably held parallel to the longitudinal axis in the opening. A coupling sleeve has first recesses corresponding to the through openings. A switching disk is rotatably arranged between a switched-on position and an idling position relative to the coupling hub. In the switched-on position, the drivers engage in the first recesses for torque transmission. When a predetermined torque is exceeded, the switching disk is transferrable from the switched-on position into the idling position by a rolling movement of the drivers. The switching disk has second recesses corresponding to the through openings. The drivers engage, in the idling position, a first spring mechanism that acts on the switching disk in the direction to the switched-on position. A second spring mechanism acts axially on the switching disk and urge the drivers against the coupling sleeve.
Torque limiting couplings are widely known from the state of the art. Forces and/or torque transmitting components of a drive train can be protected very effectively against critical loadings by the torque limiting couplings. Thus, torque limiting couplings can reduce or completely interrupt during an overload of a force- or torque transmission between a drive side and an output side of the drive train.
Document DE 30 34 606 A1 illustrates a torque limiting coupling. Here, when a predetermined torque is exceeded, the driver bodies are pushed axially against the spring force of the spring means out of the recesses and can roll-off on a side face of the coupling sleeve. Thus, the switching disk can rotate into its idling position where the driver bodies engage in recesses of the switching disk. In this position, the coupling hub is separated, drive-wise, from the coupling sleeve. Accordingly, no torque can be transmitted between the coupling hub and the coupling sleeve. Furthermore, the switching disk has, on its outer circumference, a switching cam directed radially outwards. A switching tappet is displaceably arranged between a releasing position and a locking position. The switching tappet interacts with the switching cam in the locking position. Thus, when the torque limiting coupling rotates, the switching disk is transferred into its idling position so that the torque transmission is interrupted. A return cam on the coupling hub moves the switching tappet rotating the switching disk back into the releasing position. A disadvantage of this embodiment is that after switching-off the torque limiting coupling, it is automatically switched-on again at low numbers of revolution as the switching disk is spring loaded to its torque transmitting position. Thus, the torque limiting coupling is also automatically switched-on again in an emergency situation.
Also from the document DE 102 01 988 C2, a torque limiting coupling is known. Here it is possible, when an overload occurs in a drive train with rotating components, to interrupt a force- and/or torque transmission. Further, after removing the overload, an automatic switching-on of the torque limiting coupling at low switching-on number of revolutions occurs. Generally, the switching-on number of revolutions is approximately 100 rpm. If an automatic switching-on of the torque limiting coupling is not desired, it is also possible, at very low number of revolutions, to maintain an emergency-switching-off of the torque limiting coupling. This prevents an automatic switching-on of the torque limiting coupling by means of actuating a corresponding locking pawl.
The emergency switching-off characteristic of the torque limiting coupling described in the document DE 102 01 988 C2 has, however, a disadvantage, that a switching-on of the torque transmission can only be achieved when the coupling is out of operation, namely, such that corresponding pins are manually disengaged.